I recently took my 85 Auto trans NA Z to the tranny shop,He told me it was leaking from the where the engine and the tranny meet together. Is that the rear main seal ? What would it cost to replace that. is there anything else to look for ?

 

Rear main seal is on the engine... it seals the engine oil in, not tranny fluid. If the tranny leak is internal (inside the bell housing), the trans will need to removed to find out where.

 

there is a front seal on the transmission or the rear main seal on the engine.

the transmission has transmission fluid.
the engine has oil.

you should be able to determine what's actually leaking when you pull the transmission.